In recent years, a brake override system (BOS), which prioritizes a brake operation when an accelerator operation and the brake operation are simultaneously performed, has been adopted as a control mechanism for a vehicle. The BOS limits drive force of a vehicle, for example, by decreasing the amount of opening of the throttle to a value less than the opening amount corresponding to the actual amount of the accelerator operation to reduce the engine output upon detection of simultaneous performance of the accelerator operation and the brake operation.
Meanwhile, depression force on a brake pedal is conveyed to a master cylinder. The master cylinder includes pistons, which are moved by the depressing force on the brake pedal. The movement of the pistons generates hydraulic pressure (master cylinder pressure) for actuating a braking system. A brake booster arranged between the brake pedal and the master cylinder boosts depression force on the brake pedal by intake negative pressure of the engine, and conveys the force to the master cylinder.
Patent Document 1 describes a vehicle control apparatus that calculates depression force on a brake pedal from master cylinder pressure and negative pressure of a brake booster, and utilizes the calculated force on the brake pedal as brake information.